1. Field of the Invention
The invention relates to an antenna arrangement with a plurality of radiators arranged in the form of a dipole field.
2. Discussion of the Background
An antenna, as is known from EP-A-0 098 339, is configured as a phased-array radar antenna by way of which a main lobe is generated in a chronological sequence, and in which context the generated main lobes have differing directions, in order to irradiate a section of sky. In this arrangement, where a dipole field generated by a large number of mainly horizontal dipole lines arranged one under the other, not all dipoles are connected for configuration of an overall antenna, but rather some adjacent dipoles are combined to form ancillary antennas arranged within the aperture of the main antenna, by which interferences are suppressed, which are mainly received from the main antenna because of subsidiary lobes which cannot be avoided.
The invention is based on the objective of creating an antenna arrangement including a plurality of radiators which are arranged in the form of a dipole field, for generation of a plurality of lobes in a main antenna, in which context some of the main radiators of the dipole field constitute an ancillary antenna for suppression of disturbances received by the main antenna, which can be employed as a multibeam antenna (multi-lobe antenna) in which context the capacity of a multibeam antenna includes its ability to generate simultaneously in a very precise manner, a large number of main lobes (hereafter simplified to xe2x80x9clobesxe2x80x9d).
This objective is achieved by a multibeam antenna (multi lobe antenna) configured to simultaneously generate a plurality of main lobes, wherein radiator components in the resultant dipole field, which make no significant contribution to the generation of the lobes, are included in the ancillary antenna and are fed accordingly.
An advantage of the invention resides in the fact that the ancillary antenna does not increase the size of the overall antenna arrangement.
A further advantage of the invention resides in the fact that because neither the topmost nor the bottom lines of the main antenna are used for the ancillary antenna radiators (which is also not the case in prior art), the aperture of the main antenna is largely unchanged. By suitable calculation of the power distribution to individual radiators, for example dipoles, the antenna can be selected from a wide variety of possible power distributions, in which context, for example, two lines of radiators which have spacing from the upper/lower edge of the antenna arrangement for the main antenna, are only fed with such low levels of current (or, on receive mode, for combination to produce a total signal, only such low levels of current are contributed), that the omission of these radiators will exert no practical affect on the output and directionality of the antenna. These radiators which thus provide no noticeable contribution to generation of the lobes for the main antenna and are not needed for the main antenna, are used as ancillary antennas on receive mode. The invention does not exclude co-utilization of radiators of the ancillary antenna in transmit mode for transmission, but such that they support the configuration of the lobes of the main antenna.
It may also be advantageous to implement calculation of the power distribution of individual radiators of the main antenna such that only an individual line produces no significant contribution towards the configuration of lobes, and thus only one individual line of radiators will be used as the ancillary antenna in receive mode.
It is not necessary for a complete line (or several complete lines) of radiators to configure the ancillary antenna, nor is it necessary if design considerations, particularly considerations of supply to the individual radiators should possibly make it advantageous for at least several radiators from a single line to be employed for the main antenna.
In accordance with the invention, then, it is possible to set up an antenna system in which, ifxe2x80x94for example from an elevation angle of 3xc2x0 above the plane of the horizon and below it (from this area, only disturbance signals are anticipated)xe2x80x94the reception of signals which have been received from the main antenna should be suppressed by the ancillary antenna for each individual one of the lobes operated simultaneously in the radiation curve of the main antenna, then at least one lobe of the ancillary antenna, whose elevation is for example approximately 3xc2x0, can simultaneously be generated.
In respect of the main lobes, it should also be mentioned that these are in general arranged according to several lines and columns (usually not in a precise rectilinear arangement in relation to each other), in which context the center of the main lobe of each individual lobe is at the crossover of the lines and columns.
In the case of form of embodiments in accordance with the invention, it is envisaged, for supply to the main antenna and to the ancillary antenna, that there should be a joint feed network which should ideally be constructed of Butler matrixes and Blass matrixes. The system is made up such that the transmit/receive arrangement of the antenna system is connected to input from the Blass matrixes, whose outputs are connected to inputs for the Butler matrixes whose outputs are in turn each connected to an individual radiator. Under this arrangement with a common feed matrix, there is also the option in certain operating cases, for examples in transmit mode, of using radiators of the ancillary antenna (or additional antenna) for purposes of transmission if desired.
In the example shown, the Blass matrixes bring about xe2x80x9cpivotxe2x80x9d (this is the change in direction in relation to the direction running perpendicular to the plane of the antenna aperture) in elevation, whilst the Butler matrixes bring about pivot in azimuth.
Under the other form of embodiment of the invention, on the other hand, it is envisaged that the main antenna and the additional antenna, although this is topographically arranged within the main antenna, should be fed from entirely separate feed networks.